Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (ure...

While the covalent bond plays a central role in chemical predictions, interventions, and explanations, it is a difficult concept to define precisely. This paper investigates the structural conception of the covalent bond, which says that bonding is a directional, sub-molecular region of electron density located between individual atomic centers that is responsible for holding the atoms together...

We give supporting evidence for and elaborate further on the fact [see Kreidi et al, Phys. Rev. Lett. 100, 133005 (2008)] that ionic states are essential for covalent dihydrogen H2. Kreidi et al [1] proved that interference in double photoionization of H2 results from a non-HeitlerLondon fraction of the H2 ground state, where both electrons are at the same atomic center, i.e. photoionization re...

Electronic energy (chemical bond energy) is the exclusive source of utilizable energy in biological systems. The release of this energy is mediated enzymically. The energy required to rupture a single covalent or ionic bond is prohibitively high under physiological conditions [in the range of 80-200 kcal/mol (1 kcal = 4.18 kJ)]. By the technique of the pairing of bond rupture (two juxtaposed bo...

Ionocovalency (IC), a quantitative dual nature of the atom, is defined and correlated with quantum-mechanical potential to describe quantitatively the dual properties of the bond. Orbiotal hybrid IC model scale, IC, and IC electronegativity scale, X(IC), are proposed, wherein the ionicity and the covalent radius are determined by spectroscopy. Being composed of the ionic function I and the cova...

The Bürgi-Dunitz angle (αBD) describes the trajectory of approach of a nucleophile to an electrophile. The adoption of a stereoelectronically favorable αBD can necessitate significant reactive-group repositioning over the course of bond formation. In the context of enzyme catalysis, interactions with the protein constrain substrate rotation, which could necessitate structural transformations du...

In this work, based on the experimental electron density, we present the approximate spatial distributions of the Pauli potential, one of the key quantities in the orbital-free density functional, for three crystalline systems: diamond, cubic boron nitride, and magnesium diboride. Our aim is to reveal a link between the Pauli potential and the orbital-free picture of chemical bond. We also expa...

A chemiluminescent mechanophore, bis(adamantyl-1,2-dioxetane), is used to investigate the covalent bond scission resulting from the sorption of chloroform by glassy poly(methyl methacrylate) (PMMA) networks. Bis(adamantyl)-1,2-dioxetane units incorporated as cross-linkers underwent mechanoluminescent scission, demonstrating that solvent ingress caused covalent bond scission. At higher cross-lin...